Method for reporting channel state information in wireless communication system supporting unlicensed band, and apparatus for supporting same

ABSTRACT

Disclosed are a method for a terminal to report channel state information (CSI) to a base station, and an apparatus for supporting the same. More specifically, disclosed are a method for a terminal to report CSI in a wireless communication system supporting an unlicensed band by transmitting a physical uplink shared channel (PUSCH) which only includes the CSI without an uplink shared channel (UL-SCH), and apparatuses for supporting the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2017/006687, filed on Jun. 26, 2017,which claims the benefit of U.S. Provisional Application Nos.62/357,336, filed on Jun. 30, 2016, 62/370,721, filed on Aug. 4, 2016,62/373,316, filed on Aug. 10, 2016, and 62/405,211, filed on Oct. 6,2016, the contents of which are all hereby incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication systemsupporting an unlicensed band, and more particularly, to a method ofreporting Channel State Information (CSI) to a base station by aterminal in a wireless communication system supporting an unlicensedband and apparatuses for supporting the same.

Specifically, the present invention is directed to a method in which aterminal transmits aperiodic CSI that includes only CSI without anUplink Shared Channel (UL-SCH) to a base station in a wirelesscommunication system supporting an unlicensed band and apparatuses forsupporting the same.

BACKGROUND ART

Wireless access systems have been widely deployed to provide varioustypes of communication services such as voice or data. In general, awireless access system is a multiple access system that supportscommunication of multiple users by sharing available system resources (abandwidth, transmission power, etc.) among them. For example, multipleaccess systems include a Code Division Multiple Access (CDMA) system, aFrequency Division Multiple Access (FDMA) system, a Time DivisionMultiple Access (TDMA) system, an Orthogonal Frequency Division MultipleAccess (OFDMA) system, and a Single Carrier Frequency Division MultipleAccess (SC-FDMA) system.

In addition, as more communication devices require higher communicationcapacity, the necessity of a method capable of operating communicationdevices in an accessible unlicensed band in a contention-based mannerincreases.

DISCLOSURE OF THE INVENTION Technical Task

An object of the present invention is to provide a method of reportingCSI to a base station by a terminal in a wireless communication systemsupporting an unlicensed band and apparatuses therefor.

Another object of the present invention is to provide a CSI reportingmethod for a terminal when the terminal transmits a physical uplinkshared channel including only CSI without a UL-SCH and apparatusestherefor.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

The present invention discloses a method of reporting CSI by a terminal(user equipment) in a wireless communication system supporting anunlicensed band and apparatuses therefor.

In an aspect of the present invention, provided is a method of reportingChannel State Information (CSI) by a User Equipment (UE) in a wirelesscommunication system supporting an unlicensed band. The method mayinclude: receiving, from a Base Station (BS), an uplink grant beingcomposed of a Downlink Control Information (DCI) format capable ofscheduling uplink transmission in one or more subframes in theunlicensed band; and transmitting a Physical Uplink Shared Channel(PUSCH) including the CSI without Uplink Shared Channel (UL-SCH) onlywhen the uplink grant schedules uplink transmission in a singlesubframe.

In another aspect of the present invention, provided is a User Equipment(UE) for reporting Channel State Information (CSI) in a wirelesscommunication system supporting an unlicensed band. The UE may include:a transmitter; a receiver; and a processor connected to the transmitterand the receiver. The processor may be configured to: receive, from aBase Station (BS), an uplink grant being composed of a Downlink ControlInformation (DCI) format capable of scheduling uplink transmission inone or more subframes in the unlicensed band; and transmit a PhysicalUplink Shared Channel (PUSCH) including the CSI without Uplink SharedChannel (UL-SCH) only when the uplink grant schedules uplinktransmission in a single subframe.

The uplink grant may include a CSI request bit configured to triggeraperiodic CSI reporting.

The PUSCH including the CSI without UL-SCH may be transmitted in thesingle subframe scheduled by the uplink grant.

A value of a Modulation and Coding Scheme (MCS) field in the uplinkgrant may be set to 29.

The PUSCH including the CSI without UL-SCH may be transmitted in theunlicensed band, and the UE may perform a Listen Before Talk (LBT)operation to transmit the PUSCH including the CSI with no UL-SCH in theunlicensed band.

The DCI format capable of scheduling the uplink transmission in the oneor more subframes in the unlicensed band may include DCI format 0B orDCI format 4B.

Technical solutions obtainable from the present invention arenon-limited the above-mentioned technical solutions. And, otherunmentioned technical solutions can be clearly understood from thefollowing description by those having ordinary skill in the technicalfield to which the present invention pertains.

Advantageous Effects

As is apparent from the above description, the embodiments of thepresent disclosure have the following effects.

According to the present invention, a terminal can report CSI to a basestation adaptively to a Downlink Control Information (DCI) format(s)newly defined for an unlicensed band.

In particular, if the newly defined DCI format(s) satisfiespredetermined conditions, the terminal can perform CSI reporting moreefficiently by transmitting a PUSCH including only CSI with no UL-SCH.

Effects obtainable from the present invention are non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains. That is,effects which are not intended by the present invention may be derivedby those skilled in the art from the embodiments of the presentinvention.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, provide embodiments of the presentinvention together with detail explanation. Yet, a technicalcharacteristic of the present invention is not limited to a specificdrawing. Characteristics disclosed in each of the drawings are combinedwith each other to configure a new embodiment. Reference numerals ineach drawing correspond to structural elements.

FIG. 1 is a diagram illustrating physical channels and a signaltransmission method using the physical channels;

FIG. 2 is a diagram illustrating exemplary radio frame structures;

FIG. 3 is a diagram illustrating an exemplary resource grid for theduration of a downlink slot;

FIG. 4 is a diagram illustrating an exemplary structure of an uplinksubframe;

FIG. 5 is a diagram illustrating an exemplary structure of a downlinksubframe;

FIG. 6 is a diagram illustrating the concept of dual connectivityapplicable to the present invention

FIG. 7 is a diagram illustrating an exemplary CA environment supportedin an LTE-Unlicensed (LTE-U) system;

FIG. 8 is a diagram illustrating an exemplary Frame Based Equipment(FBE) operation as one of Listen-Before-Talk (LBT) operations;

FIG. 9 is a block diagram illustrating the FBE operation;

FIG. 10 is a diagram illustrating an exemplary Load Based Equipment(LBE) operation as one of the LBT operations;

FIG. 11 is a diagram for explaining methods of transmitting a DRSsupported in an LAA system;

FIG. 12 is a flowchart for explaining CAP and CWA;

FIG. 13 is a diagram illustrating a partial TTI or a partial subframeapplicable to the present invention; and

FIG. 14 is a diagram illustrating configuration of a user equipment anda base station for implementing the proposed embodiments

BEST MODE FOR INVENTION

The embodiments of the present disclosure described below arecombinations of elements and features of the present disclosure inspecific forms. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present disclosure may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present disclosure may be rearranged. Someconstructions or elements of any one embodiment may be included inanother embodiment and may be replaced with corresponding constructionsor features of another embodiment.

In the description of the attached drawings, a detailed description ofknown procedures or steps of the present disclosure will be avoided lestit should obscure the subject matter of the present disclosure. Inaddition, procedures or steps that could be understood to those skilledin the art will not be described either.

Throughout the specification, when a certain portion “includes” or“comprises” a certain component, this indicates that other componentsare not excluded and may be further included unless otherwise noted. Theterms “unit”, “-or/er” and “module” described in the specificationindicate a unit for processing at least one function or operation, whichmay be implemented by hardware, software or a combination thereof. Inaddition, the terms “a or an”, “one”, “the” etc. may include a singularrepresentation and a plural representation in the context of the presentdisclosure (more particularly, in the context of the following claims)unless indicated otherwise in the specification or unless contextclearly indicates otherwise.

In the embodiments of the present disclosure, a description is mainlymade of a data transmission and reception relationship between a BaseStation (BS) and a User Equipment (UE). A BS refers to a terminal nodeof a network, which directly communicates with a UE. A specificoperation described as being performed by the BS may be performed by anupper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with a fixed station, aNode B, an evolved Node B (eNode B or eNB), an Advanced Base Station(ABS), an access point, etc.

In the embodiments of the present disclosure, the term terminal may bereplaced with a UE, a Mobile Station (MS), a Subscriber Station (SS), aMobile Subscriber Station (MSS), a mobile terminal, an Advanced MobileStation (AMS), etc.

A transmission end is a fixed and/or mobile node that provides a dataservice or a voice service and a reception end is a fixed and/or mobilenode that receives a data service or a voice service. Therefore, a UEmay serve as a transmission end and a BS may serve as a reception end,on an UpLink (UL). Likewise, the UE may serve as a reception end and theBS may serve as a transmission end, on a DownLink (DL).

The embodiments of the present disclosure may be supported by standardspecifications disclosed for at least one of wireless access systemsincluding an Institute of Electrical and Electronics Engineers (IEEE)802.xx system, a 3rd Generation Partnership Project (3GPP) system, a3GPP Long Term Evolution (LTE) system, and a 3GPP2 system. Inparticular, the embodiments of the present disclosure may be supportedby the standard specifications, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS36.213, 3GPP TS 36.321 and 3GPP TS 36.331. That is, the steps or parts,which are not described to clearly reveal the technical idea of thepresent disclosure, in the embodiments of the present disclosure may beexplained by the above standard specifications. All terms used in theembodiments of the present disclosure may be explained by the standardspecifications.

Reference will now be made in detail to the embodiments of the presentdisclosure with reference to the accompanying drawings. The detaileddescription, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present disclosure, rather than to show the only embodiments thatcan be implemented according to the disclosure.

The following detailed description includes specific terms in order toprovide a thorough understanding of the present disclosure. However, itwill be apparent to those skilled in the art that the specific terms maybe replaced with other terms without departing the technical spirit andscope of the present disclosure.

For example, the term, TxOP may be used interchangeably withtransmission period or Reserved Resource Period (RRP) in the same sense.Further, a Listen-Before-Talk (LBT) procedure may be performed for thesame purpose as a carrier sensing procedure for determining whether achannel state is idle or busy, CCA (Clear Channel Assessment), and CAP(Channel Access Procedure).

Hereinafter, 3GPP LTE/LTE-A systems are explained, which are examples ofwireless access systems.

The embodiments of the present disclosure can be applied to variouswireless access systems such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), etc.

CDMA may be implemented as a radio technology such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented asa radio technology such as Global System for Mobile communications(GSM)/General packet Radio Service (GPRS)/Enhanced Data Rates for GSMEvolution (EDGE). OFDMA may be implemented as a radio technology such asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA(E-UTRA), etc.

UTRA is a part of Universal Mobile Telecommunications System (UMTS).3GPP LTE is a part of Evolved UMTS (E-UMTS) using E-UTRA, adopting OFDMAfor DL and SC-FDMA for UL. LTE-Advanced (LTE-A) is an evolution of 3GPPLTE. While the embodiments of the present disclosure are described inthe context of a 3GPP LTE/LTE-A system in order to clarify the technicalfeatures of the present disclosure, the present disclosure is alsoapplicable to an IEEE 802.16e/m system, etc.

1. 3GPP LTE/LTE-A System

1.1. Overview

In a wireless access system, a UE receives information from an eNB on aDL and transmits information to the eNB on a UL. The informationtransmitted and received between the UE and the eNB includes generaldata information and various types of control information. There aremany physical channels according to the types/usages of informationtransmitted and received between the eNB and the UE.

FIG. 1 illustrates physical channels and a general signal transmissionmethod using the physical channels, which may be used in embodiments ofthe present disclosure.

When a UE is powered on or enters a new cell, the UE performs initialcell search (S12). The initial cell search involves acquisition ofsynchronization to an eNB. Specifically, the UE synchronizes its timingto the eNB and acquires information such as a cell Identifier (ID) byreceiving a Primary Synchronization Channel (P-SCH) and a SecondarySynchronization Channel (S-SCH) from the eNB.

Then the UE may acquire information broadcast in the cell by receiving aPhysical Broadcast Channel (PBCH) from the eNB.

During the initial cell search, the UE may monitor a DL channel state byreceiving a Downlink Reference Signal (DL RS).

After the initial cell search, the UE may acquire more detailed systeminformation by receiving a Physical Downlink Control Channel (PDCCH) andreceiving a Physical Downlink Shared Channel (PDSCH) based oninformation of the PDCCH (S12).

To complete connection to the eNB, the UE may perform a random accessprocedure with the eNB (S13 to S16). In the random access procedure, theUE may transmit a preamble on a Physical Random Access Channel (PRACH)(S13) and may receive a PDCCH and a PDSCH associated with the PDCCH(S14). In the case of contention-based random access, the UE mayadditionally perform a contention resolution procedure includingtransmission of an additional PRACH (S15) and reception of a PDCCHsignal and a PDSCH signal corresponding to the PDCCH signal (S16).

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S17) and transmit a Physical Uplink Shared Channel (PUSCH)and/or a Physical Uplink Control Channel (PUCCH) to the eNB (S18), in ageneral UL/DL signal transmission procedure.

Control information that the UE transmits to the eNB is genericallycalled Uplink Control Information (UCI). The UCI includes a HybridAutomatic Repeat and reQuest Acknowledgement/Negative Acknowledgement(HARQ-ACK/NACK), a Scheduling Request (SR), a Channel Quality Indicator(CQI), a Precoding Matrix Index (PMI), a Rank Indicator (RI), etc.

In the LTE system, UCI is generally transmitted on a PUCCH periodically.However, if control information and traffic data should be transmittedsimultaneously, the control information and traffic data may betransmitted on a PUSCH. In addition, the UCI may be transmittedaperiodically on the PUSCH, upon receipt of a request/command from anetwork.

FIG. 2 illustrates exemplary radio frame structures used in embodimentsof the present disclosure.

FIG. 2(a) illustrates frame structure type 1. Frame structure type 1 isapplicable to both a full Frequency Division Duplex (FDD) system and ahalf FDD system.

One radio frame is 10 ms (Tf=307200·Ts) long, including equal-sized 20slots indexed from 0 to 19. Each slot is 0.5 ms (Tslot=15360·Ts) long.One subframe includes two successive slots. An ith subframe includes2ith and (2i+1)th slots. That is, a radio frame includes 10 subframes. Atime required for transmitting one subframe is defined as a TransmissionTime Interval (TTI). Ts is a sampling time given as Ts=1/(15kHz×2048)=3.2552×10−8 (about 33 ns). One slot includes a plurality ofOrthogonal Frequency Division Multiplexing (OFDM) symbols or SC-FDMAsymbols in the time domain by a plurality of Resource Blocks (RBs) inthe frequency domain.

A slot includes a plurality of OFDM symbols in the time domain. SinceOFDMA is adopted for DL in the 3GPP LTE system, one OFDM symbolrepresents one symbol period. An OFDM symbol may be called an SC-FDMAsymbol or symbol period. An RB is a resource allocation unit including aplurality of contiguous subcarriers in one slot.

In a full FDD system, each of 10 subframes may be used simultaneouslyfor DL transmission and UL transmission during a 10-ms duration. The DLtransmission and the UL transmission are distinguished by frequency. Onthe other hand, a UE cannot perform transmission and receptionsimultaneously in a half FDD system.

The above radio frame structure is purely exemplary. Thus, the number ofsubframes in a radio frame, the number of slots in a subframe, and thenumber of OFDM symbols in a slot may be changed.

FIG. 2(b) illustrates frame structure type 2. Frame structure type 2 isapplied to a Time Division Duplex (TDD) system. One radio frame is 10 ms(Tf=307200·Ts) long, including two half-frames each having a length of 5ms (=153600·Ts) long. Each half-frame includes five subframes each being1 ms (=30720·Ts) long. An ith subframe includes 2ith and (2i+1)th slotseach having a length of 0.5 ms (Tslot=15360·Ts). Ts is a sampling timegiven as Ts=1/(15 kHz×2048)=3.2552×10−8 (about 33 ns).

A type-2 frame includes a special subframe having three fields, DownlinkPilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time Slot(UpPTS). The DwPTS is used for initial cell search, synchronization, orchannel estimation at a UE, and the UpPTS is used for channel estimationand UL transmission synchronization with a UE at an eNB. The GP is usedto cancel UL interference between a UL and a DL, caused by themulti-path delay of a DL signal.

[Table 1] below lists special subframe configurations (DwPTS/GP/UpPTSlengths).

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal Extended Normal Extended subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 ·T_(s) — — —

FIG. 3 illustrates an exemplary structure of a DL resource grid for theduration of one DL slot, which may be used in embodiments of the presentdisclosure.

Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols inthe time domain. One DL slot includes 7 OFDM symbols in the time domainand an RB includes 12 subcarriers in the frequency domain, to which thepresent disclosure is not limited.

Each element of the resource grid is referred to as a Resource Element(RE). An RB includes 12×7 REs. The number of RBs in a DL slot, NDLdepends on a DL transmission bandwidth. A structure of an uplink slotmay be identical to a structure of a downlink slot.

FIG. 4 illustrates a structure of a UL subframe which may be used inembodiments of the present disclosure.

Referring to FIG. 4, a UL subframe may be divided into a control regionand a data region in the frequency domain. A PUCCH carrying UCI isallocated to the control region and a PUSCH carrying user data isallocated to the data region. To maintain a single carrier property, aUE does not transmit a PUCCH and a PUSCH simultaneously. A pair of RBsin a subframe is allocated to a PUCCH for a UE. The RBs of the RB pairoccupy different subcarriers in two slots. Thus it is said that the RBpair frequency-hops over a slot boundary.

FIG. 5 illustrates a structure of a DL subframe that may be used inembodiments of the present disclosure.

Referring to FIG. 5, up to three OFDM symbols of a DL subframe, startingfrom OFDM symbol 0 are used as a control region to which controlchannels are allocated and the other OFDM symbols of the DL subframe areused as a data region to which a PDSCH is allocated. DL control channelsdefined for the 3GPP LTE system include a Physical Control FormatIndicator Channel (PCFICH), a PDCCH, and a Physical Hybrid ARQ IndicatorChannel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe,carrying information about the number of OFDM symbols used fortransmission of control channels (i.e. the size of the control region)in the subframe. The PHICH is a response channel to a UL transmission,delivering an HARQ ACK/NACK signal. Control information carried on thePDCCH is called Downlink Control Information (DCI). The DCI transportsUL resource assignment information, DL resource assignment information,or UL Transmission (Tx) power control commands for a UE group.

1.2. CSI Reporting

In the 3GPP LTE (-A) system, a UE is defined to report CSI to a BS(eNB). Herein, the CSI means information indicating the quality of aradio channel (also called a link) created between a UE and an antennaport. The CSI includes, for example, a Rank Indicator (RI), a PrecodingMatrix Indicator (PMI), and a Channel Quality Indicator (CQI). Herein,the RI, which indicates rank information of a channel, means the numberof streams that a UE receives on the same time-frequency resource. TheRI value is determined depending on long-term fading of the channel, andthus it is usually fed back to the BS by the UE with a longerperiodicity than that of the PMI or CQI. The PMI is a value reflectingthe channel space property and indicates a precoding index preferred bythe UE based on a metric such as a signal-to-interference-plus-noiseratio (SINR). The CQI is a value indicating the intensity of a channeland typically indicates a received SINR obtained when the BS uses thePMI.

Based on measurement of the radio channel, the UE calculates a preferredPMI and RI, which is capable of deriving the optimal or highesttransmission rate when used by the BS, in the current channel state andfeeds back the calculated PMI and RI to the BS. Herein, the CQI refersto a modulation and coding scheme of providing an acceptable packeterror probability for the fed-back PMI/RI.

The LTE-A system, where accurate MU-MIMO and explicit CoMP operationsare expected, may not sufficiently support new operations due to the CSIfeedback defined in LTE. As requirements for CSI feedback accuracy forobtaining sufficient MU-MIMO or CoMP throughput gain became complicated,it has been agreed that the PMI should be configured with a longterm/wideband PMI (W₁) and a short term/subband PMI (W₂). In otherwords, the final PMI is expressed as a function of W₁ and W₂. Forexample, the final PMI W may be defined as follows: W=W₁*W₂ or W=W₂*W₁.Accordingly, in LTE-A, the CSI may include RI, W₁, W₂ and CQI.

Table 2 below shows uplink channels used for CSI transmission in the3GPP LTE (-A) system.

TABLE 2 Periodic Aperiodic Scheduling scheme CSI transmission CSItransmission Frequency non-selective PUCCH — Frequency selective PUCCHPUSCH

Referring to Table 2, CSI may be transmitted using a Physical UplinkControl Channel (PUCCH) with a periodicity defined in higher layers.Depending on whether it is needed by a scheduler, the CSI may beaperiodically transmitted using a Physical Uplink Shared Channel(PUSCH). Transmission of the CSI over the PUSCH is possible only in thecase of frequency selective scheduling and aperiodic CSI transmission.Hereinafter, CSI transmission schemes according to scheduling schemesand periodicities will be described.

1) Transmission of CQI/PMI/RI on PUSCH after Reception of a CSITransmission Request Control Signal (CSI Request)

A PUSCH-scheduling control signal (UL grant) transmitted as a PDCCHsignal may include a control signal for requesting CSI transmission.Table 3 below shows UE modes for transmitting the CQI, PMI and RI on thePUSCH.

TABLE 3 PMI Feedback Type No PMI Single PMI Multiple PMIs PUSCH WidebandMode 1-2 CQI (Wideband CQI) RI Feed 1st wideband back CQI(4 bit) Type2nd wideband CQI(4 bit) if RI > 1 N * Subband PMI(4 bit) (N is the total# of subbands) (if 8Tx Ant, N * subband W2 + wideband W1) UE selectedMode 2-0 Mode 2-2 (Subband CQI) RI (only for RI Open-loop SM) 1stwideband 1st wideband CQI(4 bit) + Best-M CQI(4 bit) + Best-M CQI(2 bit)CQI(2 bit) 2nd wideband (Best-M CQI: CQI(4 bit) + Best-M Average CQI forM CQI(2 bit) if RI > 1 SBs selected from * Best-M index (L among total NSBs) bit) Best-M index (L Wideband bit) PMI(4 bit) + Best-M PMI(4 bit)(if 8Tx Ant, wideband W2 + Best-M W2 + wideband W1) Higher Layer- Mode3-0 Mode 3-1 Mode 3-2 configured RI (only for RI RI (Subband CQI)Open-loop SM) 1st wideband 1st wideband 1st wideband CQI(4 bit) + CQI(4bit) + CQI(4 bit) + N * subband N * subbandCQI(2 bit) N * subbandCQI(2bit) CQI(2 bit) 2nd wideband 2nd wideband CQI(4 bit) + CQI(4 bit) + N *subbandCQI(2 bit) N * subbandCQI(2 bit) if RI > 1 if RI > 1 Wideband N *Subband PMI(4 bit) PMI(4 bit) (if 8Tx Ant, (N is the total # of widebandW2 + subbands) wideband W1) (if 8Tx Ant, N * subband W2 + wideband W1)

The transmission modes of Table 3 are selected by higher layers, and theCQI/PMI/RI are all transmitted in a PUSCH subframe. Hereinafter, uplinktransmission methods performed by a UE in the individual modes will bedescribed.

Mode 1-2 represents a case where precoding matrices are selected on theassumption that data is transmitted only in subbands. A UE generates aCQI on the assumption that a precoding matrix is selected for the systemband or the entirety of a band (set S) designated by higher layers. InMode 1-2, the UE may transmit the CQI and a PMI value for each subband.In this case, the size of each subband may depend on the size of thesystem band.

In Mode 2-0, a UE may select M preferred subbands for the system band orband (set S) designated by higher layers. The UE may generate one CQIvalue on the assumption that data is transmitted for the M selectedsubbands. Preferably, the UE additionally reports one CQI (wideband CQI)value for the system band or set S. If there are multiple codewords forthe M selected subbands, the UE defines a CQI value for each codeword ina differential form.

In this case, the differential CQI value is determined as a differencebetween an index corresponding to the CQI value for the M selectedsubbands and a wideband (WB) CQI (WB-CQI) index.

The UE in mode 2-0 may transmit, to a BS, information on the locationsof the M selected subbands, one CQI value for the M selected subbands,and a CQI value generated for the entire band or designated band (setS). In this case, the size of each subband and the value of M may dependon the size of the system band.

In Mode 2-2, a UE may simultaneously select locations of M preferredsubbands and a single precoding matrix for the M preferred subbands onthe assumption that data is transmitted through the M preferredsubbands. In this case, a CQI value for the M preferred subbands isdefined per codeword. In addition, the UE additionally generates awideband CQI value for the system band or designated band (set S).

The UE in Mode 2-2 may transmit, to a BS, information on the locationsof the M preferred subbands, one CQI value for the M selected subbands,a single PMI for the M preferred subbands, a wideband PMI, and awideband CQI value. In this case, the size of a subband and the value ofM may depend on the size of the system band.

In Mode 3-0, a UE generates a wideband CQI value. The UE generates a CQIvalue for each subband on the assumption that data is transmittedthrough each subband. In this case, even if an RI>1, the CQI valuerepresents only the CQI value for the first codeword.

In Mode 3-1, a UE generates a single precoding matrix for the systemband or designated band (set S). The UE generates a CQI subband for eachcodeword by assuming the single precoding matrix generated for eachsubband. In addition, the UE may generate a wideband CQI by assuming thesingle precoding matrix. The CQI value for each subband may be expressedin a differential form. The subband CQI value is calculated as adifference between subband CQI and wideband CQI indices. In this case,the size of each subband may depend on the size of the system band.

In Mode 3-2, a UE generates a precoding matrix for each subband insteadof a single precoding matrix for the entire band, in contrast with Mode3-1.

2) Periodic CQI/PMI/RI Transmission Through PUCCH

A UE may periodically transmit CSI (e.g., CQI/PMI/PTI (precoding typeindicator) and/or RI information) to a BS on a PUCCH. If the UE receivesa control signal instructing transmission of user data, the UE maytransmit a CQI on the PUCCH. Even if the control signal is transmittedon a PUSCH, the CQI/PMI/PTI/RI may be transmitted in one of the modesdefined in Table 4 below.

TABLE 4 PMI feedback type No PMI Single PMI PUCCH CQI Wideband Mode 1-0Mode 1-1 feedback type (wideband CQI) UE selection Mode 2-0 Mode 2-1(subband CQI)

A UE may operate in transmission modes shown in Table 4. Referring toTable 4, in Mode 2-0 and Mode 2-1, a Bandwidth Part (BP) may mean a setof consecutive subbands in the frequency domain and cover the systemband or designated band (set S). In Table 3, the size of each subband,the size of a BP, and the number of BPs may depend on the size of thesystem band. In addition, the UE transmits CQIs for individual BPs inascending order in the frequency domain in order to cover the systemband or designated band (set S).

The UE may have the following PUCCH transmission types according totransmission combinations of CQI/PMI/PTI/RI.

i) Type 1: a subband CQI (SB-CQI) for Mode 2-0 and Mode 2-1 istransmitted.

ii) Type 1a: an SB CQI and a second PMI are transmitted.

iii) Types 2, 2b and 2c: a WB-CQI and PMI are transmitted.

iv) Type 2a: a WB PMI is transmitted.

v) Type 3: an RI is transmitted.

vi) Type 4: a WB CQI is transmitted.

vii) Type 5: an RI and a WB PMI are transmitted.

viii) Type 6: an RI and a PTI are transmitted.

When the UE transmits an RI and a WB CQI/PMI, the CQI/PMI aretransmitted in subframes with different periodicities and offsets. Ifthe RI needs to be transmitted in the same subframe as the WB CQI/PMI,the CQI/PMI are not transmitted.

The current LTE standard uses the 2-bit CSI request field in DCI format0 or 4 to provide aperiodic CSI feedback, considering a carrieraggregation (CA) environment. In the CA environment, if multiple servingcells are configured for a UE, the UE interprets a CSI request field astwo bits. If one of TMs 1 to 9 is set for all Component Carriers (CCs),aperiodic CSI feedback is triggered according to the values in Table 5below. And, if TM 10 is set for at least one of the CCs, the aperiodicCSI feedback is triggered according to the values in Table 6 below.

TABLE 5 CSI request field value Description ‘00’ No aperiodic CSIreporting is triggered ‘01’ Aperiodic CSI reporting is triggered for aserving cell ‘10’ Aperiodic CSI reporting is triggered for a first groupof serving cells configured by higher layers ‘11’ Aperiodic CSIreporting is triggered for a second group of serving cells configured byhigher layers

TABLE 6 CSI request field value Description ‘00’ No aperiodic CSIreporting is triggered ‘01’ Aperiodic CSI reporting is triggered for aCSI process group configured by higher layers for a serving cell ‘10’Aperiodic CSI reporting is triggered for a first group of CSI processesconfigured by higher layers ‘11’ Aperiodic CSI reporting is triggeredfor a second group of CSI processes configured by higher layers

1.3. Dual Connectivity

FIG. 6 illustrates the concept of dual connectivity applicable to thepresent invention.

Referring to FIG. 6, carrier aggregation may be performed among a macrocell 600 and small cells 610 and 620. That is, the macro cell may use ncarriers (where n is a random positive integer), and a small cell mayuse k carriers (where k is a random positive integer). In this case, thecarriers of the macro and small cells may have the same or differentfrequencies. For instance, the macro cell may use random frequencies F1and F2, and the small cell may use random frequencies F2 and F3.

A random UE in coverage of the small cell may be simultaneouslyconnected to the macro and small cells. The UE may be served by themacro and small cells at the same time or through Time DivisionMultiplexing (TDM). The UE may be served functions provided by theC-plane (e.g., connection management, mobility, etc.) through a macrocell layer. In the case of the U-plane data path, the UE may select themacro cell and/or small cell. For example, in case of real-time datasuch as Voice over LTE (VoLTE), the UE may use thereception/transmission function provided by the macro cell, which canguarantee better mobility than the small cell. For a best-effectservice, the UE may be served by the small cell. The macro and smallcells may be connected through backhaul, and the backhaul may be idealbackhaul or non-ideal backhaul.

In addition, the macro and small cells may be configured to use the samesystem, i.e., one of the TDD and FDD system. Alternatively, the macroand small cells may be configured to use different systems, that is, oneof them cell uses the TDD system and the other uses the FDD system.

The concept of the dual connectivity has been described with referenceto FIG. 6. The macro and small cells may use the same or differentfrequency bands. If a random UE is configured to operate in dualconnectivity mode, the UE may be connected to the macro and small cellsat the same time. FIG. 6 shows a case in which a small cell is set asthe U-plane data path.

Although the present invention describes that the random UE isdual-connected to the macro and small cells for convenience ofdescription, the invention is not limited to cell types (e.g., macrocell, micro cell, pico cell, femto cell, etc.). In addition, althoughthe present invention describes that the random dual-connectivity UEconfigures the carrier aggregation (CA) by setting the macro cell to aPrimary cell (Pcell) and the small cell to a Secondary cell (Scell), theinvention is not limited thereto.

2. LTE-U System

2.1. LTE-U System Configuration

Hereinafter, methods for transmitting and receiving data in a CAenvironment of an LTE-A band corresponding to a licensed band and anunlicensed band will be described. In the embodiments of the presentdisclosure, an LTE-U system means an LTE system that supports such a CAstatus of a licensed band and an unlicensed band. A WiFi band orBluetooth (BT) band may be used as the unlicensed band. LTE-A systemoperating on an unlicensed band is referred to as LAA (Licensed AssistedAccess) and the LAA may correspond to a scheme of performing datatransmission/reception in an unlicensed band using a combination with alicensed band.

FIG. 7 illustrates an example of a CA environment supported in an LTE-Usystem.

Hereinafter, for convenience of description, it is assumed that a UE isconfigured to perform wireless communication in each of a licensed bandand an unlicensed band by using two CCs. The methods which will bedescribed hereinafter may be applied to even a case where three or moreCCs are configured for a UE.

In the embodiments of the present disclosure, it is assumed that acarrier of the licensed band may be a primary CC (PCC or PCell), and acarrier of the unlicensed band may be a secondary CC (SCC or SCell).However, the embodiments of the present disclosure may be applied toeven a case where a plurality of licensed bands and a plurality ofunlicensed bands are used in a carrier aggregation method. Also, themethods suggested in the present disclosure may be applied to even a3GPP LTE system and another system.

In FIG. 7, one eNB supports both a licensed band and an unlicensed band.That is, the UE may transmit and receive control information and datathrough the PCC which is a licensed band, and may also transmit andreceive control information and data through the SCC which is anunlicensed band. However, the status shown in FIG. 7 is only example,and the embodiments of the present disclosure may be applied to even aCA environment that one UE accesses a plurality of eNBs.

For example, the UE may configure a macro eNB (M-eNB) and a PCell, andmay configure a small eNB (S-eNB) and an SCell. At this time, the macroeNB and the small eNB may be connected with each other through abackhaul network.

In the embodiments of the present disclosure, the unlicensed band may beoperated in a contention-based random access method. At this time, theeNB that supports the unlicensed band may perform a Carrier Sensing (CS)procedure prior to data transmission and reception. The CS proceduredetermines whether a corresponding band is reserved by another entity.

For example, the eNB of the SCell checks whether a current channel isbusy or idle. If it is determined that the corresponding band is idlestate, the eNB may transmit a scheduling grant to the UE to allocate aresource through (E)PDCCH of the PCell in case of a cross carrierscheduling mode and through PDCCH of the SCell in case of aself-scheduling mode, and may try data transmission and reception.

At this time, the eNB may configure a TxOP including N consecutivesubframes. In this case, a value of N and a use of the N subframes maypreviously be notified from the eNB to the UE through higher layersignaling through the PCell or through a physical control channel orphysical data channel.

2.2 Carrier Sensing (CS) Procedure

In embodiments of the present disclosure, a CS procedure may be called aClear Channel Assessment (CCA) procedure. In the CCA procedure, it maybe determined whether a channel is busy or idle based on a predeterminedCCA threshold or a CCA threshold configured by higher-layer signaling.For example, if energy higher than the CCA threshold is detected in anunlicensed band, SCell, it may be determined that the channel is busy oridle. If the channel is determined to be idle, an eNB may start signaltransmission in the SCell. This procedure may be referred to as LBT.

FIG. 8 is a view illustrating an exemplary Frame Based Equipment (FBE)operation as one of LBT operations.

The European Telecommunication Standards Institute (ETSI) regulation (EN301 893 V1.7.1) defines two LBT operations, Frame Based Equipment (FBE)and Load Based Equipment (LBE). In FBE, one fixed frame is comprised ofa channel occupancy time (e.g., 1 to 10 ms) being a time period duringwhich a communication node succeeding in channel access may continuetransmission, and an idle period being at least 5% of the channeloccupancy time, and CCA is defined as an operation for monitoring achannel during a CCA slot (at least 20 μs) at the end of the idleperiod.

A communication node periodically performs CCA on a per-fixed framebasis. If the channel is unoccupied, the communication node transmitsdata during the channel occupancy time. On the contrary, if the channelis occupied, the communication node defers the transmission and waitsuntil the CCA slot of the next period.

FIG. 9 is a block diagram illustrating the FBE operation.

Referring to FIG. 9, a communication node (i.e., eNB) managing an SCellperforms CCA during a CCA slot [S910]. If the channel is idle [S920],the communication node performs data transmission (Tx) [S930]. If thechannel is busy, the communication node waits for a time periodcalculated by subtracting the CCA slot from a fixed frame period, andthen resumes CCA [S940].

The communication node transmits data during the channel occupancy time[S950]. Upon completion of the data transmission, the communication nodewaits for a time period calculated by subtracting the CCA slot from theidle period [S960], and then resumes CCA [S910]. If the channel is idlebut the communication node has no transmission data, the communicationnode waits for the time period calculated by subtracting the CCA slotfrom the fixed frame period [S940], and then resumes CCA [S910].

FIG. 10 is a view illustrating an exemplary LBE operation as one of theLBT operations.

Referring to FIG. 10(a), in LBE, the communication node first sets q(q∈{4, 5, . . . , 32}) and then performs CCA during one CCA slot.

FIG. 10(b) is a block diagram illustrating the LBE operation. The LBEoperation will be described with reference to FIG. 10(b).

The communication node may perform CCA during a CCA slot [S1010]. If thechannel is unoccupied in a first CCA slot [S1020], the communicationnode may transmit data by securing a time period of up to (13/32)q ms[S1030].

On the contrary, if the channel is occupied in the first CCA slot, thecommunication node selects N (N∈{1, 2, . . . , q}) arbitrarily (i.e.,randomly) and stores the selected N value as an initial count. Then, thecommunication node senses a channel state on a CCA slot basis. Each timethe channel is unoccupied in one specific CCA slot, the communicationnode decrements the count by 1. If the count is 0, the communicationnode may transmit data by securing a time period of up to (13/32)q ms[S1040].

2.3 Discontinuous Transmission in DL

When discontinuous transmission is performed on an unlicensed carrierhaving a limited maximum transmission period, the discontinuoustransmission may influence on several functions necessary for performingan operation of LTE system. The several functions can be supported byone or more signals transmitted at a starting part of discontinuous LAADL transmission. The functions supported by the signals include such afunction as AGC configuration, channel reservation, and the like.

When a signal is transmitted by an LAA node, channel reservation has ameaning of transmitting signals via channels, which are occupied totransmit a signal to other nodes, after channel access is performed viaa successful LBT operation.

The functions, which are supported by one or more signals necessary forperforming an LAA operation including discontinuous DL transmission,include a function for detecting LAA DL transmission transmitted by a UEand a function for synchronizing frequency and time. In this case, therequirement of the functions does not mean that other availablefunctions are excluded. The functions can be supported by other methods.

2.3.1 Time and Frequency Synchronization

A design target recommended by LAA system is to support a UE to make theUE obtain time and frequency synchronization via a discovery signal formeasuring RRM (radio resource management) and each of reference signalsincluded in DL transmission bursts, or a combination thereof. Thediscovery signal for measuring RRM transmitted from a serving cell canbe used for obtaining coarse time or frequency synchronization.

2.3.2 DL Transmission Timing

When a DL LAA is designed, it may follow a CA timing relation betweenserving cells combined by CA, which is defined in LTE-A system (Rel-12or earlier), for subframe boundary adjustment. Yet, it does not meanthat a base station starts DL transmission only at a subframe boundary.Although all OFDM symbols are unavailable in a subframe, LAA system cansupport PDSCH transmission according to a result of an LBT operation. Inthis case, it is required to support transmission of control informationnecessary for performing the PDSCH transmission.

2.4 Measuring and Reporting RRM

LTE-A system can transmit a discovery signal at a start point forsupporting RRM functions including a function for detecting a cell. Inthis case, the discovery signal can be referred to as a discoveryreference signal (DRS). In order to support the RRM functions for LAA,the discovery signal of the LTE-A system and transmission/receptionfunctions of the discovery signal can be applied in a manner of beingchanged.

2.4.1 Discovery Reference Signal (DRS)

A DRS of LTE-A system is designed to support on/off operations of asmall cell. In this case, off small cells correspond to a state thatmost of functions are turned off except a periodic transmission of aDRS. DRSs are transmitted at a DRS transmission occasion with a periodof 40, 80, or 160 ms. A DMTC (discovery measurement timingconfiguration) corresponds to a time period capable of anticipating aDRS received by a UE. The DRS transmission occasion may occur at anypoint in the DMTC. A UE can anticipate that a DRS is continuouslytransmitted from a cell allocated to the UE with a correspondinginterval.

If a DRS of LTE-A system is used in LAA system, it may bring newconstraints. For example, although transmission of a DRS such as a veryshort control transmission without LBT can be permitted in severalregions, a short control transmission without LBT is not permitted inother several regions. Hence, a DRS transmission in the LAA system maybecome a target of LBT.

When a DRS is transmitted, if LBT is applied to the DRS, similar to aDRS transmitted in LTE-A system, the DRS may not be transmitted by aperiodic scheme. In particular, it may consider two schemes described inthe following to transmit a DRS in the LAA system.

As a first scheme, a DRS is transmitted at a fixed position only in aDMTC configured on the basis of a condition of LBT.

As a second scheme, a DRS transmission is permitted at one or moredifferent time positions in a DMTC configured on the basis of acondition of LBT.

As a different aspect of the second scheme, the number of time positionscan be restricted to one time position in a subframe. If it is moreprofitable, DRS transmission can be permitted at the outside of aconfigured DMTC as well as DRS transmission performed in the DMTC.

FIG. 11 is a diagram for explaining DRS transmission methods supportedby LAA system.

Referring to FIG. 11, the upper part of FIG. 11 shows the aforementionedfirst scheme for transmitting a DRS and the bottom part of FIG. 11 showsthe aforementioned second scheme for transmitting a DRS. In particular,in case of the first scheme, a UE can receive a DRS at a positiondetermined in a DMTC period only. On the contrary, in case of the secondscheme, a UE can receive a DRS at a random position in a DMTC period.

In LTE-A system, when a UE performs RRM measurement based on DRStransmission, the UE can perform single RRM measurement based on aplurality of DRS occasions. In case of using a DRS in LAA system, due tothe constraint of LBT, it is difficult to guarantee that the DRS istransmitted at a specific position. Even though a DRS is not actuallytransmitted from a base station, if a UE assumes that the DRS exists,quality of an RRM measurement result reported by the UE can bedeteriorated. Hence, when LAA DRS is designed, it is necessary to permitthe existence of a DRS to be detected in a single DRS occasion. By doingso, it may be able to make the UE combine the existence of the DRS withRRM measurement, which is performed on successfully detected DRSoccasions only.

Signals including a DRS do not guarantee DRS transmissions adjacent intime. In particular, if there is no data transmission in subframesaccompanied with a DRS, there may exist OFDM symbols in which a physicalsignal is not transmitted. While operating in an unlicensed band, othernodes may sense that a corresponding channel is in an idle state duringa silence period between DRS transmissions. In order to avoid theabovementioned problem, it is preferable that transmission burstsincluding a DRS signal are configured by adjacent OFDM symbols in whichseveral signals are transmitted.

2.5 Channel Access Procedure and Contention Window Adjustment Procedure

In the following, the aforementioned channel access procedure and thecontention window adjustment procedure are explained in the aspect of atransmission node.

FIG. 12 is a flowchart for explaining CAP and CWA.

In order for an LTE transmission node (e.g., a base station) to operatein LAA Scell(s) corresponding to an unlicensed band cell for DLtransmission, it may initiate a channel access procedure (CAP) [S1210].

The base station can randomly select a back-off counter N from acontention window (CW). In this case, the N is configured by an initialvalue Ninit [S1220]. The Ninit is randomly selected from among valuesranging from 0 to CW_(p).

Subsequently, if the back-off counter value (N) corresponds to 0[S1222], the base station terminates the CAP and performs Tx bursttransmission including PSCH [S1224]. On the contrary, if the back-offvalue is not 0, the base station reduces the back-off counter value by 1[S1230].

The base station checks whether or not a channel of the LAA Scell(s) isin an idle state [S1240]. If the channel is in the idle state, the basestation checks whether or not the back-off value corresponds to 0[S1250]. The base station repeatedly checks whether or not the channelis in the idle state until the back-off value becomes 0 while reducingthe back-off counter value by 1.

In the step S1240, if the channel is not in the idle state i.e., if thechannel is in a busy state, the base station checks whether or not thechannel is in the idle state during a defer duration (more than 15 usec)longer than a slot duration (e.g., 9 usec) [S1242]. If the channel is inthe idle state during the defer duration, the base station can resumethe CAP [S1244]. For example, when the back-off counter value Ninitcorresponds to 10, if the channel state is determined as busy after theback-off counter value is reduced to 5, the base station senses thechannel during the defer duration and determines whether or not thechannel is in the idle state. In this case, if the channel is in theidle state during the defer duration, the base station performs the CAPagain from the back-off counter value 5 (or, from the back-off countervalue 4 by reducing the value by 1) rather than configures the back-offcounter value Ninit. On the contrary, if the channel is in the busystate during the defer duration, the base station performs the stepS1242 again to check whether or not the channel is in the idle stateduring a new defer duration.

Referring back to FIG. 11, the base station checks whether or not theback-off counter value (N) becomes 0 [S1250]. If the back-off countervalue (N) becomes 0, the base station terminates the CAP and may be ableto transmit a Tx burst including PDSCH.

The base station can receive HARQ-ACK information from a UE in responseto the Tx burst [S1270]. The base station can adjust a CWS (contentionwindow size) based on the HARQ-ACK information received from the UE[S1280].

In the step S1280, as a method of adjusting the CWS, the base stationcan adjust the CWS based on HARQ-ACK information on a first subframe ofa most recently transmitted Tx burst (i.e., a start subframe of the Txburst).

In this case, the base station can set an initial CW to each priorityclass before the CWP is performed. Subsequently, if a probability thatHARQ-ACK values corresponding to PDSCH transmitted in a referencesubframe are determined as NACK is equal to or greater than 80%, thebase station increases CW values set to each priority class to a nexthigher priority.

In the step S1260, PDSCH can be assigned by a self-carrier schedulingscheme or a cross-carrier scheduling scheme. If the PDSCH is assigned bythe self-carrier scheduling scheme, the base station counts DTX,NACK/DTX, or ANY state among the HARQ-ACK information fed back by the UEas NACK. If the PDSCH is assigned by the cross-carrier schedulingscheme, the base station counts the NACK/DTX and the ANY states as NACKand does not count the DTX state as NACK among the HARQ-ACK informationfed back by the UE.

If bundling is performed over M (M>=2) number of subframes and bundledHARQ-ACK information is received, the base station may consider thebundled HARQ-ACK information as M number of HARQ-ACK responses. In thiscase, it is preferable that a reference subframe is included in the Mnumber of bundled subframes.

2.6. Channel Access Priory Class

TABLE 7 Channel Access Priority allowed Class (p) m_(p) CW_(min, p)CW_(max, p) T_(m cot, p) CW_(p) sizes 1 1 3 7 2 ms {3, 7} 2 1 7 15 3 ms{7, 15} 3 3 15 63 8 or 10 ms {15, 31, 63} 4 7 15 1023 8 or 10 ms {15,31, 63, 127, 255, 511, 1023}

As shown in Table 7, in Rel-13 LAA system, 4 channel access priorityclasses are defined in total. And, a length of a defer period, a CWS,MCOT (maximum channel occupancy time), and the like are definedaccording to each of the channel access priority classes. Hence, when aneNB transmits a downlink signal via an unlicensed band, the eNB performsrandom backoff by utilizing LBT parameters determined according to achannel access priority class and may be then able to access a channelduring limited maximum transmission time only after the random backoffis completed.

For example, in case of the channel access priority class 1/2/3/4, themaximum channel occupancy time (MCOT) is determined by 2/3/8/8 ms. Themaximum channel occupancy time (MCOT) is determined by 2/3/10/10 ms inenvironment where other RAT such as Wi-Fi does not exists (e.g., bylevel of regulation).

As shown in Table 7, a set of CWSs capable of being configured accordingto a class is defined. One of points different from Wi-Fi system is inthat a different backoff counter value is not defined according to achannel access priority class and LBT is performed using a singlebackoff counter value (this is referred to as single engine LBT).

For example, when an eNB intends to access a channel via an LBToperation of class 3, since CWmin (=15) is configured as an initial CWS,the eNB performs random backoff by randomly selecting an integer fromamong numbers ranging from 0 to 15. If a backoff counter value becomes0, the eNB starts DL Tx and randomly selects a new backoff counter for anext Tx burst after the DL Tx burst is completed. In this case, if anevent for increasing a CWS is triggered, the eNB increases a size of theCWS to 31 corresponding to a next size, randomly selects an integer fromamong numbers ranging from 0 to 31, and performs random backoff.

In this case, when a CWS of the class 3 is increased, CWSs of allclasses are increased as well. In particular, if the CW of the class 3becomes 31, a CWS of a class 1/2/4 becomes 7/15/31. If an event fordecreasing a CWS is triggered, CWS values of all classes are initializedby CWmin irrespective of a CWS value of the triggering timing.

2.7. Subframe Structure Applicable to LAA System

FIG. 13 is a diagram illustrating a partial TTI or a partial subframeapplicable to the present invention.

In Rel-13 LAA system, MCOT is utilized as much as possible when DL Txburst is transmitted. In order to support consecutive transmission, apartial TTI, which is defined as DwPTS, is introduced. The partial TTI(or partial subframe) corresponds to a section in which a signal istransmitted as much as a length shorter than a legacy TTI (e.g., lms)when PDSCH is transmitted.

In the present invention, for clarity, a starting partial TTI or astarting partial subframe corresponds to a form that a part of symbolspositioned at the fore part of a subframe are emptied out. An endingpartial TTI or an ending partial subframe corresponds to a form that apart of symbols positioned at the rear part of a subframe are emptiedout. (On the contrary, an intact TTI is referred to as a normal TTI or afull TTI.)

FIG. 13 illustrates various types of the aforementioned partial TTI. Thefirst drawing of FIG. 13 illustrates an ending partial TTI (or subframe)and the second drawing illustrates a starting partial TTI (or subframe).The third drawing of FIG. 13 illustrates a partial TTI (or subframe)that a part of symbols positioned at the fore part and the rear part ofa subframe are emptied out. In this case, when signal transmission isexcluded from a normal TTI, a time section during which the signaltransmission is excluded is referred to as a transmission gap (TX gap).

Although the present invention is explained on the basis of a DLoperation in FIG. 13, the present invention can also be identicallyapplied to a UL operation. For example, a partial TTI structure shown inFIG. 13 can be applied to a form of transmitting PUCCH or PUSCH as well.

3. Proposed Embodiment

Based on the above technical discussion, the present invention proposesmethods in which a UE performs periodic CSI transmission and aperiodicCSI transmission in a CA environment including LAA SCells.

3.1. Periodic CSI (pCSI) Transmission

Before describing pCSI transmission at a UE according to the presentinvention, the pCSI transmission methods in the legacy LTE system willbe described.

<pCSI Transmission Methods in the Legacy LTE System>

(1) PUCCH format 1/2

(A) If aperiodic CSI is triggered, pCSI is dropped.

(B) If simultaneous transmission of PUCCH/PUSCH is configured on,

1) if there is HARQ-ACK to be transmitted,

A) if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured on,

1> if there is a scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 1 and the pCSI is transmitted on the PUSCH.

2> if there is no scheduled PUSCH, the HARQ-ACK and pCSI is transmittedusing PUCCH format 2.

B) if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured off,

1> if there is a scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 1 and the pCSI is transmitted on the PUSCH.

2> if there is no scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 1 and the pCSI is dropped.

2) if there is no HARQ-ACK to be transmitted, the pCSI is transmittedusing PUCCH format 2.

(C) If simultaneous transmission of PUCCH/PUSCH is configured off,

1) if there is a scheduled PUSCH, the pCSI is transmitted on a PUSCHwith the lowest SCell index (lowest SCellIndex cell PUSCH).

2) if there is no scheduled PUSCH,

A) if there is HARQ-ACK to be transmitted,

1> if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured on, the HARQ-ACK and pCSI is transmitted using PUCCH format2.

2> if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured off, the HARQ-ACK is transmitted using PUCCH format 1 and thepCSI is dropped.

B) if there is no HARQ-ACK to be transmitted, the pCSI is transmittedusing PUCCH format 2.

(2) PUCCH format 3

(A) If aperiodic CSI is triggered, pCSI is dropped.

(B) If simultaneous transmission of PUCCH/PUSCH is configured on,

1) if there is HARQ-ACK to be transmitted,

A) if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured on,

1> if there is a scheduled PUSCH, the HARQ-ACK is transmitted in PUSCCHformat 3 and the pCSI is transmitted on the PUSCH.

2> if there is no scheduled PUSCH, the HARQ-ACK and pCSI is transmittedusing PUCCH format 3.

B) if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured off,

1> if there is a scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 3 and the pCSI is transmitted on the PUSCH.

2> if there is no scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 3 and the pCSI is dropped.

2) if there is no HARQ-ACK to be transmitted, the pCSI is transmittedusing PUCCH format 2.

(C) If simultaneous transmission of PUCCH/PUSCH is configured off,

1) if there is a scheduled PUSCH, the pCSI is transmitted on a PUSCHcorresponding to a cell with the lowest SCell index (lowest SCellIndexcell).

2) if there is no scheduled PUSCH,

A) if there is HARQ-ACK to be transmitted,

1> if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured on, the HARQ-ACK and pCSI is transmitted using PUCCH format3.

2> if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured off, the HARQ-ACK is transmitted using PUCCH format 3 and thepCSI is dropped.

B) if there is no HARQ-ACK to be transmitted, the pCSI is transmittedusing PUCCH format 2.

(3) PUCCH format 4/5

(A) If aperiodic CSI is triggered, pCSI is dropped.

(B) If simultaneous transmission of PUCCH/PUSCH is configured on,

1) if there is HARQ-ACK to be transmitted,

A) if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured on,

1> if there is a scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 4/5 and the pCSI is transmitted on the PUSCH.

2> if there is no scheduled PUSCH, the HARQ-ACK and pCSI is transmittedusing PUCCH format 4/5.

B) if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured off,

1> if there is a scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 4/5 and the pCSI is transmitted on the PUSCH.

2> if there is no scheduled PUSCH, the HARQ-ACK is transmitted usingPUCCH format 4/5 and the pCSI is dropped.

2) if there is no HARQ-ACK to be transmitted, the pCSI is transmittedusing PUCCH format 2 or PUCCH format 4/5.

(C) If simultaneous transmission of PUCCH/PUSCH is configured off,

1) if there is a scheduled PUSCH, the pCSI is transmitted on a PUSCHcorresponding to a cell with the lowest SCell index (lowest SCellIndexcell).

2) if there is no scheduled PUSCH,

A) if there is HARQ-ACK to be transmitted,

1> if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured on, the HARQ-ACK and pCSI is transmitted using PUCCH format4/5.

2> if simultaneous transmission of the pCSI and HARQ-ACK on the PUCCH isconfigured off, the HARQ-ACK is transmitted using PUCCH format 4/5 andthe pCSI is dropped.

B) if there is no HARQ-ACK to be transmitted, the pCSI is transmittedusing PUCCH format 2 or PUCCH format 4/5.

Additionally, the eLAA system in Release 14 considers supportingsimultaneous transmission of a PUCCH in a licensed band (or licensedcarrier) and a PUSCH in an unlicensed band (or LAA SCell) at all timesfor UL transmission at a UE. Considering the simultaneous transmission,if a UE is configured to transmit HARQ-ACK and pCSI in a specificsubframe and an unlicensed band (e.g., LAA SCell) PUSCH is scheduled inthe specific subframe in a CA environment including an unlicensed band(e.g., LAA SCell), the UE, which operates according to the legacy LTEsystem, may transmit the pCSI on a PUSCH in a cell with the lowest Scellindex among scheduled PUSCHs other than the following exceptional case.

(Exceptional case) When HARQ-ACK transmission is performed using PUCCHformat 4/5, if simultaneous transmission of PUCCH/PUSCH is configuredand simultaneous transmission of HARQ-ACK and CSI is also configured oractivated (that is, if the value of a parameter namedsimultaneousAckNackAndCQI-Format4-Format5-r13 is set to ‘TRUE’), a UEtransmits pCSI on a PUCCH rather than a PUSCH.

<pCSI Transmission Methods for a UE According to the Present Invention>

The present invention does not consider the above exceptional case. Thisis because since in the exceptional case, pCSI is transmitted on a PUCCHrather than a PUSCH, a UE can transmit the pCSI on a PUCCH in a licensedband if the exceptional case is applied. In other words, the presentinvention proposes a particular method for transmitting pCSI on a PUSCHin a CA environment including LAA SCells, and thus in the exceptionalcase where pCSI is transmitted on a PUCCH rather than a PUSCH, a UE canoperate in the same way as in the legacy LTE system.

Hereinafter, methods in which a UE transmits pCSI in a specific subframewhen the UE needs to perform HARQ-ACK transmission and pCSI reporting inthe specific subframe in a CA environment including LAA SCells will bedescribed in detail.

3.1.1. First pCSI Transmission Method

According to the present invention, when PUSCHs are scheduled inlicensed bands (or licensed carriers) and LAA SCells, a UE may beconfigured to transmit HARQ-ACK and pCSI first on a licensed band (orlicensed carrier) PUSCH. That is, the UE may transmit the HARQ-ACK andpCSI through a PUSCH in a cell with the lowest SCell index among thelicensed bands (or licensed carriers) except the LAA SCells. By doingso, it is possible to eliminate the uncertainty of pCSI transmission,which results from the characteristics of an LAA SCell where PUSCHtransmission is allowed only when a UE successfully completes ListenBefore Talk (LBT).

However, when only LAA SCell PUSCHs are allocated without schedulinglicensed band (or licensed carrier) PUSCHs (a first case) or when a cellwith the lowest SCell index is an LAA SCell (unlike the above case)although PUSCHs are scheduled in licensed bands (or licensed carriers)and LAA SCells (a second case), pCSI transmission methods can bedetermined as follows. In addition, a different pCSI transmission methodcan be applied to each case.

3.1.2. Second pCSI Transmission Method

A UE drops pCSI transmission. In other words, in one of the above cases,the UE may drop the pCSI transmission.

3.1.3. Third pCSI Transmission Method

A UE attempt to transmit pCSI on the assumption that no PUSCH isallocated. For example, when a UE transmits HARQ-ACK using PUCCH format4/5 (if simultaneous transmission of PUCCH/PUSCH is configured and thevalue of the parameter namedsimultaneousAckNackAndCQI-Format4-Format5-r13 is set to ‘TRUE’), the UEmay transmit the HARQ-ACK together with pCSI using PUCCH format 4/5 asif there is no scheduled PUSCH. And, the UE may transmit a UL-SCH onlywithout UCI piggyback on an LAA SCell using a PUSCH. As another example,when a UE transmits HARQ-ACK using PUCCH format 4/5 (if simultaneoustransmission of PUCCH/PUSCH is configured and the value of the parameternamed simultaneousAckNackAndCQI-Format4-Format5-r13 is set to ‘FALSE’),the UE may transmit the HARQ-ACK using PUCCH format 4/5 and drop pCSItransmission as if there is no scheduled PUSCH. And, the UE may transmita UL-SCH only without UCI piggyback on an LAA SCell using a PUSCH.

3.1.4. Fourth pCSI Transmission Method

A UE may perform pCSI transmission on an LAA SCell. For example, pCSImay be configured to be transmitted only in a cell with the lowest SCellindex. In this case, if the UE fails LBT for the corresponding cell, theUE should drop the pCSI transmission. To compensate for the pCSItransmission drop, which occurs when the UE fails LBT, the UE mayperform HARQ-ACK and pCSI transmission on PUSCHs in all available LAASCells.

In addition, the UE may transmit the pCSI on a cell with the lowestSCell index among LAA SCells where there is ongoing transmission.Moreover, the UE may attempt the pCSI transmission on not only the cellwith the lowest SCell index but N LAA SCells selected in ascending indexorder.

3.2. Aperiodic CSI (aCSI) Transmission without UL-SCH

Before describing aCSI transmission methods according to the presentinvention, the methods of performing aCSI transmission with no UL-SCHdefined in the legacy LTE system will be described.

In the legacy LTE system, if a UE receives a UL grant satisfying thefollowing conditions, the UE may transmit a PUSCH including only a ULcontrol indicator (e.g., UCI, HARQ-ACK, CQI, PMI, RI, etc.) without aUL-SCH.

(1) A case in which DCI format 0 is used and I_mcs=29 or a case in whichDCI format 4 is used, I_mcs=29, and only one Transmission Block (TB) isenabled.

The condition that DCI format 4 is used and only one TB is enabled maysatisfy either {I_mcs=0 and N_prb>1} or {I_mcs=28 and N_prb=1}. In thiscase, I_mcs indicates a Modulation and Coding Scheme (MCS) index and mayhave a value in the range of 0 to 31. N_prb indicates the number ofPhysical Resource Blocks (PRBs) where one or two TB s are scheduled.

If 2-TB transmission is scheduled, I_mcs may be indicated for each TB,and common N_prb may be indicated for all TBs. In this case, if thecondition of {I_mcs=0 and N_prb>1} is satisfied, the indicatedmodulation orders and coding rates are not suitable for the 2-TBtransmission so that it could be interpreted to mean that only one TB isenabled. In addition, if the condition of {I_mcs=28 and N_prb=1} issatisfied, the indicated modulation orders and coding rates haveextremely high values and only a single RB is scheduled so that it couldbe interpreted to mean that only one TB is enabled due to a small amountof available information.

In DL, the condition for disabling one TB is that I_mcs=0 and RedundancyVersion (RV)=1.

(2) A case in which aCSI reporting is triggered by the “CSI request” bitfield

(3) If there is only one serving cell, the condition of N_prb<4 shouldbe met. If a serving cell is configured with CA composed of two to fiveCCs, the condition of N_prb<20 should be met. However, if a serving isconfigured with CA composed of five or more CCs, aCSI transmission ispossible without any UL-SCHs regardless of the value of N_prb.

Meanwhile, in the LAA system to which the present invention isapplicable, the following matters are introduced or modified compared tothe legacy LTE system. Thus, the conditions for a UL grant that triggerstransmission of a PUSCH including only CSI with no UL-SCH may bemodified in the LAA system according to the present invention.

1> Asynchronous HARQ is introduced in UL transmission, and an RV valueis separately signaled. Thus, I_mcs=29/30/31, which respectivelyrepresented RV=1/2/3 in the legacy system, may be modified torespectively represent modulation order 2/4/6 for retransmission in theLAA system to which the present invention is applicable, similar to thatin DL.

2> New DCI format 0A/0B/4A/4B is defined for the LAA system to which thepresent invention is applicable. Specifically, DCI format 0A/4A is toschedule a single subframe, and more particularly, DCI format 0A is usedfor 1-TB transmission and DCI format 4A is used for 2-TB transmission.In addition, DCI format 0B/4B is to schedule multiple subframes, andmore particularly, DCI format 0B is used for 1-TB transmission and DCIformat 4B is used for 2-TB transmission. In this case, the maximumnumber of subframes that can be scheduled by DCI format 0B/4B isconfigurable, and the maximum number of subframes may be set to one of2, 3, and 4. Moreover, DCI format 0B/4B may also be used to scheduleonly a single subframe.

In particular, the “RV” bit field of DCI format 0A/4A may be composed of2/4 bit. Using DCI format 0A/4A, an eNB may signal four RV values perTB.

In addition, the “RV” bit field of DCI format 0B/4B may be composed ofbits corresponding to the maximum number of schedulable subframes. Inthis case, each RV value may be commonly applied to TBs, and the RVvalue may be set to 0 or 2. For example, if the maximum number ofsubframes that can be scheduled by DCI format 4B is 3, the “RV” bitfield of DCI format 4B is composed of 3 bits. Each bit indicates thatthe RV is 0 or 2 for a subframe mapped to each bit, and two TBs sharethe same RV value.

3> In the LAA system to which the present invention is applicable, PUSCHresource allocation may be performed on an interlace basis. In thiscase, one interlace may be composed of 10 RBs which are equallydistributed. Specifically, the one interlace may be composed of 10 RBsspaced at intervals of 10 RBs. Thus, the minimum unit of N_prb is 10,and the PUSCH resource allocation may be performed using a multiple of10.

4> When aCSI reporting is triggered by the “CSI request” bit field ofDCI format 0B/4B, aCSI may be reported in the last subframe if thenumber of scheduled subframes is equal to or less than 2, and the aCSImay be reported in the second last subframe if the number of scheduledsubframes is equal to or more than 3.

Since the LAA system to which the present invention is applicable isquite different from the legacy LTE system as described above, thepresent invention proposes the following conditions as the conditionsfor a UL grant triggering transmission of a PUSCH including only CSIwith no UL-SCH by considering the differences therebetween. In thiscase, the PUSCH including only CSI with no UL-SCH may be transmittedwhen some or all of the following conditions are satisfied.

3.2.1. First Condition

The first condition may be that in the case of using DCI format 4A/4B,which is the DCI format for 2-TB transmission, only one TB is enabled.To this end, the condition of I_mcs=0 may be applied.

In this case, in the case of using DCI format 4A, I_mcs=0 and RV=1 (asan additional condition) may be applied to satisfy the condition thatonly one TB is enabled.

Alternatively, the following TB disabling methods may be applied toenable only one TB. In this case, one or any combination of thefollowing methods may be applied in order to disable one TB.

1) Considering that the minimum unit of N_prb is 10 regarding the PUSCHresource allocation in the LAA system to which the present invention isapplicable, one TB may be disabled if either {I_mcs=0 and N_prb>10} or{I_mcs=28 and N_prb=10} is satisfied.

Additionally, an RV condition may be considered as the condition fordisabling one TB. For example, in addition to condition 1), if an RVvalue is set to 1 in the case of using DCI format 4A or if an RV valueis set to 2 in the case of using DCI format 4B, one TB may be disabled.Alternatively, the RV condition may be commonly configured for DCIformat 4A/4B (for example, RV value=2).

2) Similar to the legacy LTE system, if I_mcs=0 and the RV condition ismet, one TB may be disabled.

In this case, the RV condition may depend on whether the DCI format iseither DCI format 4A or DCI format 4B. For example, when DCI format 4Ais used, the RV condition may be satisfied if the RV value is 1, andwhen DCI format 4B is used, the RV condition may be satisfied if the RVvalue is 2. As another example, the RV condition may be commonlyconfigured for DCI format 4A/4B (for example, RV value=2).

3) A new 1-bit indicator indicating that one TB is disabled may beintroduced. Alternatively, among the fields included in a UL grant,reserved bits may be used to disable one TB.

3.2.2. Second Condition

The second condition may be that an I_mcs parameter value is set to oneof {29, 30, 31}.

For example, among I_mcs parameter values used for retransmission, theI_mcs parameter value corresponding to modulation order 6 (for example,31) may be used as the second condition. This is because the probabilityof instructing transmission with modulation order 6 is relatively low.

3.2.3. Third Condition

The third condition may be established such that the correspondingcondition is regardless of the value of N_prb. Alternatively, the thirdcondition may be established such that only when the number of CSIprocesses is more than 5, it is regardless of the value of N_prb butotherwise, the condition of N_prb=10 or N_prb<=10 (or the condition thatonly a single interlace is allocated) is applied.

3.2.4. Fourth Condition

As the fourth condition, constraint conditions depending on the numberof scheduled subframes may be applied. This is because scheduling aPUSCH with no UL-SCH in multiple consecutive subframes is not desirablein terms of system implementation. Hereinafter, the constraintconditions corresponding to the fourth condition will be described indetail.

(1) Only DCI format 0A/4A can be used. More specifically, when DCIformat 0B/4B is used, transmission of a PUSCH including only CSI with noUL-SCH may not be allowed.

(2) DCI format 0B (and/or DCI format 4B) as well as DCI format 0A/4A canbe used. However, when DCI format 0B (and/or DCI format 4B) is used,only one subframe should be scheduled. That is, when only one subframeis scheduled by DCI format 0B/4B, transmission of a PUSCH including onlyCSI with no UL-SCH may be allowed.

(3) DCI format 0B (and/or DCI format 4B) as well as DCI format 0A/4A canbe used. However, when DCI format 0B (and/or DCI format 4B) is used, thenumber of actually scheduled subframes should be less than the maximumnumber of schedulable subframes. In this case, transmission of a PUSCHincluding only CSI with no UL-SCH is performed on a subframe next to theactually scheduled subframes (or a later subframe), and transmission ofa PUSCH without aCSI may be performed on the actually scheduledsubframes.

(4) DCI format 0B (and/or DCI format 4B) as well as DCI format 0A/4A canbe used. However, similar to the existing aCSI transmission rule, whenDCI format 0B (and/or DCI format 4B) is used, a PUSCH including only CSIwith no UL-SCH is transmitted in the last subframe if the number ofactually scheduled subframes is equal to or less than 2. On thecontrary, if the number of actually scheduled subframes is equal to ormore than 3, the PUSCH including only the CSI with no UL-SCH istransmitted in the second last subframe. In this case, that is, when thePUSCH including only the CSI with no UL-SCH is transmitted in the secondlast subframe, the HARQ process index of the last subframe may beconfigured by excluding or including the second last subframe. Forexample, if the number of scheduled subframes is 4 and the HARQ processindex is set to 3, the HARQ process indices corresponding to theindividual scheduled subframes are 3/4/5/6, respectively. In this case,when a PUSCH including only CSI with no UL-SCH is transmitted in thesecond last subframe, the HARQ process index of the last subframe may beset to 6 as it is or 5 by excluding the subframe where the transmissionis performed with no UL-SCH.

(5) DCI format 0B (and/or DCI format 4B) as well as DCI format 0A/4A canbe used. However, when DCI format 0B (and/or DCI format 4B) is used, aPUSCH including only CSI with no UL-SCH may be transmitted in the firstor last (or a specific) subframe (SF) among scheduled subframe(s). Ifthe PUSCH including only the CSI with no UL-SCH is transmitted in thefirst subframe among the scheduled subframe(s), the HARQ process indexof the second subframe may be configured by excluding or including thefirst subframe.

For example, if the number of scheduled subframes is 4 and the HARQprocess index is set to 3, the HARQ process indices corresponding to theindividual scheduled subframes may be 3/4/5/6, respectively. In thiscase, when a PUSCH including only CSI with no UL-SCH is transmitted inthe first subframe, the HARQ process index of the second subframe may beset to 4 as it is or 3 by excluding the subframe where the transmissionis performed with no UL-SCH.

The fourth condition may vary depending on whether DCI format 0B or 4Bis used. For example, in the case of using DCI format 0B, the fourthcondition may be applied as described in (3) or (4). In the case ofusing DCI format 4B, the fourth condition may be applied as described in(2).

3.2.5. Fifth Condition

The fifth condition may be that aCSI reporting is triggered by the “CSIrequest” bit field.

3.2.6. Sixth Condition

As the sixth condition, constraint conditions for RV values may beapplied.

For example, in the case of using DCI format 0A/4A, the condition thatan RV value is set to 1 or 2 (for common design with DCI format 0B/4B)may be applied as the sixth condition.

As another example, in the case of using DCI format 0B/4B, the conditionthat an RV value is set to 2 and/or some or all of the RV valuescorresponding to non-scheduled subframes are set to 2 may be applied asthe sixth condition.

3.2.7. Seventh Condition

The seventh condition may be the combination of the above-describedfourth and sixth conditions. The seventh condition may be applied tomulti-subframe DCI, that is, when DCI format 0B/4B is used.

(1) If the condition described in (5) of the fourth condition issatisfied, a PUSCH including only CSI with no UL-SCH may be transmittedin the first or last (or a specific) subframe among scheduledsubframe(s). Particularly, a rule may be configured as follows: if thenumber of actually scheduled subframes is less than 3, the aCSI istransmitted in the last subframe, and if the number of actuallyscheduled subframes is equal to or more than 3, the aCSI is transmittedin the second last subframe.

In this case, a rule may be configured as follows: if the RV value forthe subframe where the PUSCH including only the aCSI with no UL-SCH isto be transmitted satisfies the above-described sixth condition (as wellas some or all of the first, second, third, and fifth conditions), thePUSCH including only the aCSI with no UL-SCH is transmitted in thecorresponding subframe.

(2) A rule may be configured as follows: a PUSCH including only aCSIwith no UL-SCH is transmitted in a subframe(s) that satisfies the sixthcondition (as well as some or all of the first, second, third, and fifthconditions). In this case, to improve the inefficiency that multiplesubframes are used to report the same aCSI, a set of CCs for the aCSItransmission may vary per scheduled subframe. For example, the “CSIreporting” bit field may be allocated differently depending on thenumber of scheduled subframes (or the maximum number of scheduledsubframes).

Specifically, when the size of the “CSI reporting” bit field is 2 bits,if the number of scheduled subframes (or the maximum number of scheduledsubframes) is 3, the “CSI reporting” bit field may be composed of atotal of 6 bits. In this case, aCSI corresponding to a set of CCsindicated by the “CSI reporting” bit field, which correspond to thelocation of each subframe, may be transmitted in a subframe(s) thatsatisfies the sixth condition (as well as some or all of the first,second, third, and fifth conditions).

As another example, the bit-width of the “CSI reporting” bit field maybe constant, but a set of CCs corresponding to aCSI transmission mayvary per scheduled subframe according to a predetermined rule.Specifically, a rule may be configured as follows: if ‘10’ is signaledby the “CSI reporting” bit field and there are multiple subframessatisfying the sixth condition (as well as some or all of the first,second, third, and fifth conditions), ‘10’ is applied to the firstsubframe, ‘11’ is applied to the second subframe, and ‘01’ is applied tothe third subframe.

(3) A rule may be configured as follows: a PUSCH including only aCSIwith no UL-SCH is transmitted in a subframe(s) that satisfies the sixthcondition (as well as some or all of the first, second, third, and fifthconditions). In this case, if there are multiple subframes satisfyingthe corresponding conditions, the PUSCH including only the aCSI with noUL-SCH may be transmitted in one specific subframe among the subframes.For example, the corresponding specific subframe may be set to the firstor last subframe among the subframes that satisfy the sixth condition(as well as some or all of the first, second, third, and fifthconditions).

3.3. aCSI and pCSI Transmission Methods

In this section, how a UE configured to perform UL transmission on anLAA SCell performs pCSI and/or aCSI transmission if the pCSItransmission collides with the aCSI transmission on the same subframewill be described.

In particular, the present invention describes pCSI and/or aCSItransmission methods when pCSI transmission on an L-cell is configuredand aCSI transmission on a U-cell is triggered. In the legacy LTEsystem, when pCSI and aCSI transmission collides to each other on thesame subframe, a UE drops the pCSI transmission and performs the aCSItransmission only.

3.3.1 First aCSI and pCSI Transmission Method

A UE determines whether to perform transmission on a U-cell according toits LBT result. Therefore, if the UE drops pCSI transmission and failsLBT in a corresponding subframe, the UE may not attempt not only thepCSI transmission but aCSI transmission. To prevent the occurrence ofthis situation, the present invention proposes a method for allowingpCSI transmission on an L-cell and aCSI transmission on a U-cell at thesame time. In other words, if a UE succeeds LBT on a U-cell where aCSItransmission is triggered, the UE may perform pCSI transmission on anL-cell and the aCSI transmission on the U-cell. On the other hand, ifthe UE fails the LBT on the U-cell where the aCSI transmission istriggered, the UE may only perform the pCSI transmission on the L-cell.

3.3.2. Second aCSI and pCSI Transmission Method

As an extreme example, when a UE performs aCSI and pCSI transmissionaccording to the above-described first aCSI and pCSI transmissionmethod, the UE may redundantly report pCSI and aCSI using CSI on thesame serving cell. Considering that this operation not only correspondsto new UE behavior, which is not defined in the legacy LTE system, buttransmits the same CSI, it may not be desirable.

Thus, if a cell for pCSI reporting is equivalent to a cell(s) for aCSIreporting (or if these cells overlap each other or are in a mutualinclusion relation), the UE may be configured to drop the pCSItransmission. In other words, if the cell for pCSI reporting is notequivalent to the cell(s) for aCSI reporting (or if these cells do notoverlap), the aforementioned first aCSI and pCSI transmission method maybe applied.

The second aCSI and pCSI transmission method can be applied even whensimultaneous transmission of pCSI on a random cell and aCSI on anothercell is allowed in the same subframe, regardless of cell types (e.g.,L-cell, U-cell, etc.).

3.3.3. Third aCSI and pCSI Transmission Method

When a UE performs aCSI and pCSI transmission according to theabove-described first aCSI and pCSI transmission method, the totalnumber of CSI processes that the UE should report may exceed the maximumnumber of CSI processes where the UE can perform CSI update (or CSImeasurement) (for example, 5 CSI processes in case CA is composed of 5CCs or less and a value reported by UE capability signaling in case CAis composed of more than 5 CCs). To overcome this problem, the thirdaCSI and pCSI transmission method proposes to drop the pCSI transmissionin the above situation.

In other words, if the total number of CSI processes that should bereported does not exceed the maximum number of CSI processes where a UEcan perform CSI update (or CSI measurement) (for example, 5 CSIprocesses in case CA is composed of 5 CCs or less and a value reportedby UE capability signaling in case CA is composed of more than 5 CCs),the UE may perform aCSI and pCSI transmission according to theabove-described first aCSI and pCSI transmission method.

The corresponding method can be applied when simultaneous transmissionof pCSI on a random cell and aCSI on another cell is allowed in the samesubframe, regardless of cell types (e.g., L-cell, U-cell, etc.).

The aforementioned first to third aCSI and pCSI transmission methods canbe applied to the dual connectivity situation (when a PUCCH cell groupis configured or when the stand-alone operation where only a U-cell isused without assistance from an L-cell is supported). For example, inthe case of a Secondary Cell Group (SCG) consisting of only U-cells (orPUCCH Cell Group (CG)), if pCSI transmission collides with aCSItransmission in the same subframe, a UE may simultaneously perform pCSIand aCSI transmission according to the first aCSI and pCSI transmissionmethod. In other words, in this case, the UE may be allowed tosimultaneously perform the pCSI and aCSI transmission according to thefirst aCSI and pCSI transmission method of the present invention.

Since each of the examples of the proposed methods can be considered asone method for implementing the present invention, it is apparent thateach example can be regarded as a proposed method. In addition, it ispossible to implement the proposed methods not only independently but bycombining (or merging) some of the proposed methods. Moreover, a rulemay be defined such that information on whether the proposed methods areapplied (or information on rules related to the proposed methods) shouldbe transmitted from a BS to a UE through a predefined signal (e.g.,physical layer signal, higher layer signal, etc.).

As described above, the present invention provides methods in which a UEreports CSI using an unlicensed band in a wireless communication systemsupporting the unlicensed band.

Due to the nature of the unlicensed band, the UE may receive a UL grantbeing composed of a DCI format (e.g., DCI format 0B/4B) capable ofscheduling UL transmission in at least one subframe in the unlicensedband.

In this case, the UL grant may include a CSI request bit configured totrigger aCSI reporting and an MCS field set to a specific value (e.g.,29).

Upon receiving the UL grant, the UE may transmit a UL signal (e.g.,PUSCH) in the at least one subframe indicated by the UL grant on theunlicensed band. In particular, the UE may perform LBT for thetransmission on the unlicensed band, and based on the LBT result, the UEmay transmit the UL signal in the at least one subframe scheduled by theUL grant.

In this case, if the UL grant triggers the aCSI reporting by schedulingUL transmission in a single subframe even though it can schedule aplurality of subframes, the UE can transmit the CSI on a PUSCH withoutUL-SCH to a BS. In other words, the UE may transmit the PUSCH includingonly the CSI without UL-SCH if specific conditions are satisfied.

Therefore, according to the present invention, when the aCSI reportingis triggered and the specific conditions are satisfied, the UE canreport the CSI to the BS more efficiently

4. Device Configuration

FIG. 14 is a diagram illustrating configurations of a UE and a basestation capable of being implemented by the embodiments proposed in thepresent invention. The UE shown in FIG. 14 operates to implement theembodiments of the aforementioned CSI reporting methods

A UE 1 may act as a transmission end on a UL and as a reception end on aDL. A base station (eNB) 100 may act as a reception end on a UL and as atransmission end on a DL.

That is, each of the UE and the base station may include a Transmitter(Tx) 10 or 110 and a Receiver (Rx) 20 or 120, for controllingtransmission and reception of information, data, and/or messages, and anantenna 30 or 130 for transmitting and receiving information, data,and/or messages.

Each of the UE and the base station may further include a processor 40or 140 for implementing the afore-described embodiments of the presentdisclosure and a memory 50 or 150 for temporarily or permanently storingoperations of the processor 40 or 140.

With the above-described configuration, the UE 1 may be configured toreceive a UL grant being composed of a DCI format capable of schedulingUL transmission in at least one subframe in an unlicensed band throughthe receiver 20 and transmit a PUSCH including CSI without UL-SCHthrough the transmitter 20 only when the UL grant schedules ULtransmission in one subframe. In this case, the PUSCH including the CSIwithout UL-SCH is transmitted in the unlicensed band, and to this end,the UE may perform Listen Before Talk (LBT) operation to transmit thePUSCH including the CSI with no UL-SCH in the unlicensed band.

The Tx and Rx of the UE and the base station may perform a packetmodulation/demodulation function for data transmission, a high-speedpacket channel coding function, OFDM packet scheduling, TDD packetscheduling, and/or channelization. Each of the UE and the base stationof FIG. 14 may further include a low-power Radio Frequency(RF)/Intermediate Frequency (IF) module.

Meanwhile, the UE may be any of a Personal Digital Assistant (PDA), acellular phone, a Personal Communication Service (PCS) phone, a GlobalSystem for Mobile (GSM) phone, a Wideband Code Division Multiple Access(WCDMA) phone, a Mobile Broadband System (MBS) phone, a hand-held PC, alaptop PC, a smart phone, a Multi Mode-Multi Band (MM-MB) terminal, etc.

The smart phone is a terminal taking the advantages of both a mobilephone and a PDA. It incorporates the functions of a PDA, that is,scheduling and data communications such as fax transmission andreception and Internet connection into a mobile phone. The MB-MMterminal refers to a terminal which has a multi-modem chip built thereinand which can operate in any of a mobile Internet system and othermobile communication systems (e.g. CDMA 2000, WCDMA, etc.).

Embodiments of the present disclosure may be achieved by various means,for example, hardware, firmware, software, or a combination thereof.

In a hardware configuration, the methods according to exemplaryembodiments of the present disclosure may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the methods according to theembodiments of the present disclosure may be implemented in the form ofa module, a procedure, a function, etc. performing the above-describedfunctions or operations. A software code may be stored in the memory 180or 190 and executed by the processor 120 or 130. The memory is locatedat the interior or exterior of the processor and may transmit andreceive data to and from the processor via various known means.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentdisclosure or included as a new claim by a subsequent amendment afterthe application is filed.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention can be applied to variouswireless access systems including 3GPP (3rd Generation PartnershipProject) and 3GPP2 system. The embodiments of the present invention canbe applied not only to various wireless access systems but also to alltechnical fields to which the various wireless access systems areapplied. Further, the proposed method can also be applied to an mmWavecommunication system using ultrahigh frequency band.

What is claimed is:
 1. A method for operating a User Equipment (UE) in awireless communication system, the wireless communication systemincluding a base station (BS) and supporting communications in anunlicensed band, the method performed by the UE and comprising:receiving, from the BS, an uplink (UL) grant for scheduling an uplinktransmission in the unlicensed band, wherein the UL grant includesdownlink control information (DCI), the DCI including information forscheduling a transmission of a Physical Uplink Shared Channel (PUSCH)that includes aperiodic channel state information (CSI); based on the ULgrant, transmitting the PUSCH to the BS, wherein the PUSCH only includesthe aperiodic CSI, and is transmitted in a single subframe, based on: avalue of a Modulation and Coding Scheme (MCS) field included in the DCI,a CSI request bit included in the DCI, and a number of subframes to beused for the PUSCH being set to 1, wherein the number of scheduledsubframes being set to 1 is included in the DCI when the DCI correspondsto a first specific DCI format, or the number of scheduled subframesbeing set to 1 is preassigned when the DCI corresponds to a secondspecific DCI format, wherein the first specific DCI format is DCI format0B or 4B, wherein the second specific DCI format is DCI format 0A or 4A,and wherein the MCS field value is
 29. 2. A User Equipment (UE) foroperating in a wireless communication system, the wireless communicationsystem including a base station (BS) and supporting communications in anunlicensed band, the UE comprising: a memory; a transceiver; and aprocessor operatively connected to the memory and the transceiver, theprocessor for: receiving, from the BS, an uplink (UL) grant forscheduling an uplink transmission in the unlicensed band, wherein the ULgrant includes downlink control information (DCI), the DCI includinginformation for scheduling a transmission of a Physical Uplink SharedChannel (PUSCH) that includes aperiodic channel state information (CSI);based on the UL grant, transmitting the PUSCH to the BS, wherein thePUSCH only includes the aperiodic CSI, and is transmitted in a singlesubframe, based on: a value of a Modulation and Coding Scheme (MCS)field included in the DCI, a CSI request bit included in the DCI, and anumber of subframes to be used for the PUSCH being set to 1, wherein thenumber of scheduled subframes being set to 1 is included in the DCI whenthe DCI corresponds to a first specific DCI format, or the number ofscheduled subframes being set to 1 is preassigned when the DCIcorresponds to a second specific DCI format, wherein the first specificDCI format is DCI format 0B or 4B, wherein the second specific DCIformat is DCI format 0A or 4A, and wherein the MCS field value is
 29. 3.A method for operating a base station (BS) in a wireless communicationsystem, the wireless communication system including a User Equipment(UE) and supporting communications in an unlicensed band, the methodperformed by the BS and comprising: transmitting, to the UE, an uplink(UL) grant for scheduling an uplink transmission in the unlicensed band,wherein the UL grant includes downlink control information (DCI), theDCI including information for scheduling a transmission of a PhysicalUplink Shared Channel (PUSCH) that includes aperiodic channel stateinformation (CSI); based on the UL grant, receiving the PUSCH from theUE, wherein the PUSCH only includes the aperiodic CSI, and istransmitted in a single subframe, based on: a value of a Modulation andCoding Scheme (MCS) field included in the DCI, a CSI request bitincluded in the DCI, and a number of subframes to be used for the PUSCHbeing set to 1, wherein the number of scheduled subframes being set to 1is included in the DCI when the DCI corresponds to a first specific DCIformat, or the number of scheduled subframes being set to 1 ispreassigned when the DCI corresponds to a second specific DCI format,wherein the first specific DCI format is DCI format 0B or 4B, whereinthe second specific DCI format is DCI format 0A or 4A, and wherein theMCS field value is
 29. 4. A base station (BS) for operating in awireless communication system, the wireless communication systemincluding a User Equipment (UE) and supporting communications in anunlicensed band, the BS comprising: a memory; a transceiver; and aprocessor operatively connected to the memory and the transceiver, theprocessor for: transmitting, to the UE, an uplink (UL) grant forscheduling an uplink transmission in the unlicensed band, wherein the ULgrant includes downlink control information (DCI), the DCI includinginformation for scheduling a transmission of a Physical Uplink SharedChannel (PUSCH) that includes aperiodic channel state information (CSI);based on the UL grant, receiving the PUSCH from the UE, wherein thePUSCH only includes the aperiodic CSI, and is transmitted in a singlesubframe, based on: a value of a Modulation and Coding Scheme (MCS)field included in the DCI, a CSI request bit included in the DCI, and anumber of subframes to be used for the PUSCH being set to 1, wherein thenumber of scheduled subframes being set to 1 is included in the DCI whenthe DCI corresponds to a first specific DCI format, or the number ofscheduled subframes being set to 1 is preassigned when the DCIcorresponds to a second specific DCI format, wherein the first specificDCI format is DCI format 0B or 4B, wherein the second specific DCIformat is DCI format 0A or 4A, and wherein the MCS field value is 29.